Composition for substrate materials and process for the same as well as a heat conductive substrate and process for the same

ABSTRACT

A composition for substrate materials according to the present invention includes 70 - 95 wt. % of inorganic powder and 5 - 30 wt. % of thermosetting resin composition and is in a finely crushed condition. The composition for substrate materials is prepared, for example, by crushing into fine pieces and mixing the inorganic powder and the thermosetting resin composition. A heat conductive substrate is provided with an insulator body formed by heating and pressurizing said composition for substrate materials and a wiring pattern is provided in such a condition that it is exposed on the surface of the insulator body. A process for manufacturing the heat conductive substrate comprises forming said composition for substrate materials into the insulator body by casting the above mentioned composition for substrate materials into a metal mold to be heated and pressurized so that said thermosetting resin is cured.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a composition for substratematerials and process for the same, as well as a heat conductivesubstrate and process for the same, particularly to a technology forgaining a heat conductive substrate preferably utilized in the field ofpower electronics.

[0003] 2. Description of the Related Art

[0004] Accompanying with the increased performance or miniaturization ofelectronic equipment, it is desired for semiconductor devices orelectronic parts to be designed more densely or to be improved inperformance. It is also desired for circuit substrates on whichsemiconductor devices or electronic components are mounted to bedesigned more densely and more miniaturized. Therefore it has becomeimportant to design a circuit substrate taking account of heatradiation. The following is an example of a heat conductive substratewhich is a circuit substrate improved in heat radiating performance.This heat conductive substrate has a configuration where the wiringpattern is formed through an insulator layer on one or two sides of ametal plate such as copper or aluminum. In the following, this heatconductive substrate is referred to as a insulated metal substrate.

[0005] On the other hand, as an example of a heat conductive substrateimproved in the heat radiating performance there is a heat conductivesubstrate in which a copper plate is integrated with a ceramic substrateformed of alumina, aluminum nitride or the like. In the following such aheat conductive substrate is referred to as a metal-attached ceramicsubstrate.

[0006] As for a metal-based substrate, it is preferable to make theinsulator layer thinner to secure a better heat radiation. To make theinsulator layer thinner, however, leads to disadvantages such that itbecomes more susceptible to the effect of the noise or it becomes moredifficult to secure enough withstand voltage against insulation.

[0007] And metal attached ceramic substrate can only be utilized forhigh current because of the reason that a manufacturing cost is highercompared to that of a metal-based substrate, therefore it is general touse a metal-based substrate for other objects.

[0008] In this way, it is difficult to achieve metal-based substratesand metal-attached ceramic substrates which satisfy both functions andmanufacturing costs.

[0009] Therefore, in recent years, the following manufacturing processof heat conducting substrates is proposed. First of all, a resincomposition where an inorganic filler with heat conductivity is filledup in a thermoplastic resin is prepared. And by injection molding andintegrating this resin composition and a lead frame, a heat conductivemodule-type heat conductive substrate is formed.

[0010] Though a heat conductive module type heat conductive substratemanufactured in this manner can be secured in the mechanical strengthbetter than that of metal-attached ceramic substrate, there occurs adisadvantage that heat radiation is worse because it is difficult tofill up inorganic filler in high density. The following is the reasonwhy it is difficult to fill up inorganic filler in high density. Toomuch amount of filler increases the melting viscosity dramatically andmakes it difficult to carry out kneading and injection molding. Andbecause the filler works as an abrasive, the aberration of the metalmold is significant.

[0011] Therefore, recently, a heat conductive substrate manufactured byforming resin composition filled up with inorganic filler with good heatradiation integrated with a lead frame is proposed, as disclosed in, forexample, the Japanese unexamined patent publication H10 (1998) -173097.

[0012] This heat conductive substrate is manufactured with the methodshown in FIG. 9. That is to say, a mixture slurry including at leastsome inorganic filler and thermosetting resin is prepared. By forming afilm from this mixture slurry a green sheet 31 is manufactured. Afterdrying the green sheet 31, as shown in FIG. 9A, the green sheet 31 andthe lead frame 32 are overlapped. After that, the green sheet 31 iscured by heating and pressurizing to produce a heat conductive substrate34 constructed from a heat conductive cured body 33 and the lead frame32 attached and integrated together, as shown in FIG. 9B.

[0013] In the above mentioned conventional heat conductive substrate 34,however, the following disadvantages occur. First, the green sheet 31cannot be arranged without forming space with the lead frame 32 with thecomplicated form and the form precision cannot be fully maintained.

[0014] Moreover, in order to control the sheet thickness whilemanufacturing sheets, it is necessary to control and adjust theviscosity of the mixture slurry and a film-forming device, and work forthat is difficult.

[0015] In addition, the sheet cutting process such as die punching usinga metal mold for the convenience of processing sheets into a desiredshape is indispensable, and therefore the processes have increased toraise the manufacturing costs.

[0016] In addition, the sheets cut off from the necessary parts cannotbe utilized and they become dispensable, so it is not onlydisadvantageous from the point of cost effectiveness but also theresource is not utilized effectively.

SUMMARY OF THE INVENTION

[0017] Therefore, the main object of the present invention is to providea heat conductive substrate with excellent heat radiation that ispossible to be formed into a complicated form and the process for thesame.

[0018] Another object of the present invention is to provide a processfor a heat conductive substrate where control of mixture slurry or afilm-forming device as well as sheet processing or the like areunnecessary.

[0019] Still another object of the present invention is to provide acomposition for substrate materials configured such that a heatconductive substrate can be manufactured easily and economically as wellas the manufacturing process for the same.

[0020] To achieve the above-mentioned objects, a composition forsubstrate materials of the present invention includes 70 - 95 wt. % ofinorganic powder and 5 - 30 wt. % of thermosetting resin composition andis in a condition of crushed fine pieces. By using this composition forsubstrate materials, by curing the thermosetting resin on condition thatinorganic powder is included in high density, a heat conductivesubstrate with good heat radiation including a high density of inorganicpowder can easily be manufactured. Such a heat conductive substrateallows semi-conductor devices to be mounted directly thereon, and isextremely preferable as a heat conductive substrate used in the field ofpower electronics because it has a thermal expansion coefficient in theplane direction very close to that of semi-conductors.

[0021] And because the composition for substrate materials is in acondition of crushed fine pieces, it is possible for it to be filledwith high precision even in a metal mold of complicated structure underthe influence of the finely shaped lead frame or the like. In addition,it is possible to be filled in and be formed with the minimum amount ofthe composition for substrate materials to cause no waste of thecomposition for substrate materials. Moreover, such a formation with ahigh precision can be implemented under the conditions of lowtemperature and low pressure. The condition of finely crushed pieces ispreferably a powder condition or a granulation condition.

[0022] It also preferable to coat the inorganic powder withthermosetting resin composition, thereby the adhesive properties betweeninorganic powder grains would be excellent.

[0023] It is also preferable for the thermosetting resin composition tobe in a B-stage condition, thereby, as a result of less stickiness ofthe composition for substrate materials, it becomes easy to be handled.

[0024] It is also preferable for the inorganic powder to be at least onekind chosen among Al₂O₃, MgO, BN and AlN, thereby it gives the inorganicpowder an excellent electric insulation and heat conductivity.

[0025] It is also preferable for the grain diameter of the inorganicpowder to be within the range of 0.1 - 100 μm, thereby being able toprevent the heat radiation from lowering. The larger grain diameters ofthe inorganic powder than this range would lower the density andtherefore lowers the heat radiation. On the other hand, too small graindiameters would require to increase resin amount in order to fullycontact powder grains with each other as a result of the increasedsurface area as a whole, which prevents the density from increasing andtherefore lowers the heat radiation.

[0026] Moreover it is preferable that the thermosetting resincomposition includes at least one kind of thermosetting resin chosenfrom among epoxy resin, phenol resin, cyanate resin as the maincomponent, or that the thermosetting resin composition includesbrominated polyfunctional epoxy resin as the main component, and, inaddition, includes a bisphenol A-type novolac resin as a curing agentand imidazol as a curing accelerator.

[0027] In addition, it is preferable imidazol to be micro-encapsulated,thereby the storage stability for the composition for substratematerials would be improved because the curing accelerator doesn't reactwith the thermosetting resin until the formation of the heat conductivesubstrate.

[0028] It is preferable to add to the thermosetting resin composition atleast one kind chosen from among a coupling agent, a dispersing agent, acoloring agent and a mold-releasing agent.

[0029] According to a manufacturing process of the composition forsubstrate materials of the present invention, 70 to 95 wt. % ofinorganic powder and 5 to 30 wt. % of thermosetting resin compositionincluding thermosetting resin which is in a solid condition at a roomtemperature are crushed into fine pieces and mixed.

[0030] A manufacturing process of a composition for substrate materialsaccording to the present invention includes a process of manufacturing amixture by mixing 70 to 95 wt. % of inorganic powder and 5 to 30 wt. %of thermosetting resin composition including thermosetting resin whichis in a liquid condition at a room temperature and a process forcrushing said mixture into fine pieces after granulating it.

[0031] A manufacturing of a composition for substrate materialsaccording to the present invention has a process for mixing 70 to 95 wt.% of inorganic powder and 5 to 30 wt. % of thermosetting resincomposition including thermosetting resin which is in a liquid conditionat a room temperature and a process for turning said thermosetting resininto a B-stage by heat treating the mixture manufactured in the aboveprocess under temperature conditions lower than the curing temperatureof said thermosetting resin and a process for crushing into fine piecessaid mixture in which said heat setting resin composition is turned intoa B-stage.

[0032] A manufacturing process of a composition for substrate materialsaccording to the present invention has a process for mixing 70 to 95 wt.% of inorganic powder and 5 to 30 wt. % of thermosetting resincomposition including thermosetting resin with solvent in which saidthermosetting resin is dissolved and a process for drying the mixturemanufactured in the above process at a lower temperature than the curingtemperature of the said thermosetting resin to remove said solvent fromsaid mixture and a process for crushing said mixture said solvent isremoved from into fine pieces.

[0033] According to those manufacturing processes, a composition forsubstrate materials for manufacturing a heat conductive substrate can beextremely easily manufactured.

[0034] A heat conductive substrate according to the present inventionhas an insulation body formed, by heating and pressurizing, from acomposition for substrate materials including 70 to 95 wt. % ofinorganic powder having electric insulation and 5 to 30% ofthermosetting resin composition and being in a condition of crushed finepieces. This heat conductive substrate could secure good heat radiationwhile securing excellent mechanical strength.

[0035] It is also preferable for the wiring pattern to be provided onthe condition that it is exposed on the surface of said insulator body.Said wiring pattern is preferably a lead frame. It is also preferablethat a metal plate for heat radiation is provided on the condition thatit is exposed on the surface of said insulator body.

[0036] A manufacturing process for heat conductive substrate accordingto the present invention has the first process where a composition forsubstrate materials including 70 to 95 wt. % of inorganic powder havingelectric insulation and 5 to 30% of thermosetting resin composition andbeing in a condition of crushed fine pieces is cast into a metal moldand the second process where said composition for substrate materials isformed into an insulator body by heating and pressurizing saidcomposition for substrate materials within the metal mold to cure saidthermosetting resin.

[0037] According to this manufacturing process, it is possible tomanufacture a heat conductive substrate having complicated shape easilyand with high precision without requiring control of slurry or afilm-forming device, sheet processing or the like.

[0038] It is preferable that the pressure in which said composition forsubstrate materials are heated and pressurized is within the range of 1to 20 MPa.

[0039] It is preferable that the temperature in which said compositionfor substrate materials are heated and pressurized is within the rangeof 140 to 260° C.

[0040] It is preferable that, in said first process, said compositionfor substrate materials is cast into said metal mold while arranging alead frame in the metal mold in advance and, in said second process,said insulator body and lead frame are formed and integrated by heatingand pressurizing said composition for substrate materials. Or it ispreferable that, in said first process, a lead frame is arranged in saidmetal mold in which said composition for substrate materials are castand, in said second process, said insulator body and said lead frame areformed and integrated by heating and pressurizing said composition forsubstrate materials. By doing those processes, the composition forsubstrate materials goes into the gaps created by the lead frame havingmicro-structured and complicated form so that the insulator body and thelead frame are surely integrated. In addition, it is possible to formwith minimum amount of composition for substrate materials filled in sothat no waste results from the composition for substrate materials. Inaddition, because such a formation can be carried out under theconditions of low temperature and low pressure, not only is iteconomical but it also has the following advantages.

[0041] In an injection mold or the like which is a general formingmethod, extremely large injection pressure is applied so that the resinshould be spread into every corner of the metal mold. Therefore, in casea heat conductive substrate with a lead frame is formed by injectionmold or the like, the resin reaches onto the surface of the lead frame,which makes it necessary to set up a process for removing this extraresin after the forming process.

[0042] Contrary to that, because the composition for the substratematerials has a form of finely crushed pieces, the composition forsubstrate materials can be spread into every corner including the gapswith the lead frame by applying little pressure on casting thecomposition for substrate materials into the metal mold. Therefore,extra resin would not go onto the surface of the lead frame exposing theinsulator body. Accordingly it is not necessary to have a process forremoving such extra resin.

[0043] To resolve the disadvantages of the above mentioned injectionmold, there is a method to integrate the green sheet described in theprior art and the lead frame. In this method, however, the green sheetcannot be fitted into the parts with complicated forms and the followingdisadvantages are included.

[0044] In a heat conductive substrate, it is desired to have a thicklead frame because of the reason that heat radiation should be enhancedor high current should be applied. In the method using the green sheet,however, the formation precision cannot be maintained when the leadframe is thick because the heat conductive substrate is manufactured bypushing the green sheet into the gap with the lead frame.

[0045] On the contrary, according to the present invention, thecomposition for substrate materials can be spread into every corner inthe gaps created by a thick lead frame because finely crushedcomposition for substrate materials is cast into a metal mold so that itcan be applied for a thick lead frame.

[0046] It is preferable that, in said first process, a metal plate forheat radiation is arranged within said metal mold in which saidcomposition for substrate materials is cast and, in said second process,said composition for substrate materials is heated and pressurized tomold integrally said insulator body and said metal plate. Or it ispreferable that, in said first process, a metal plate for heat radiationis arranged in advance within the metal mold and then said compositionfor substrate materials is cast into the metal mold and, in said secondprocess, by heating and pressurizing said composition for substratematerials, said insulator body and said metal plate are moldedintegrally. In this manner, the metal plate for heat radiation isintegrated into the insulator body.

[0047] Moreover, in the first process, a metal foil is arranged in saidmetal mold in advance then said composition for substrate materials iscast into the metal mold and, in said second process, by heating andpressurizing said composition for substrate materials, the insulationbody and said metal foil are molded integrally and then said metal foilis pattern-processed into a wiring pattern. Or it is preferable that, insaid first process, a metal foil may be arranged in the metal mold afterthe composition for substrate materials is cast therein and in saidsecond process, by heating and pressurizing said composition forsubstrate materials said heat conductive substrate and said metal foilare molded integrally and then said metal foil may be pattern-processedinto a wiring pattern.

[0048] It is preferable that said metal foil is copper foils with athickness of 12 to 200 μm and is roughened at least on the surfacefacing the composition for substrate materials. Thereby, the adhesivestrength with the insulator body would be enhanced.

[0049] Here a room temperature is generally specified to be atemperature range between about −10 to 40° C.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Other objects of the present invention will be clarified uponunderstanding the embodiments described hereinafter and be specified inthe attached claims. And a number of advantages the presentspecification does not touch on will be brought to mind by those skilledin the art upon implementing this invention.

[0051]FIG. 1 is an explanatory diagram illustrating the firstmanufacturing process on manufacturing the composition for substratematerials according to the first preferable embodiment of the presentinvention;

[0052]FIG. 2 is an explanatory diagram illustrating the secondmanufacturing process on manufacturing the composition for substratematerials according to the first preferable embodiment;

[0053]FIG. 3 is an explanatory diagram illustrating the thirdmanufacturing process on manufacturing the composition for substratematerials according to the first preferable embodiment;

[0054]FIG. 4 is an explanatory diagram illustrating the fourthmanufacturing process on manufacturing the composition for substratematerials according to the first preferable embodiment;

[0055]FIG. 5 is an explanatory diagram illustrating the firstmanufacturing process on manufacturing a heat conductive substrateaccording to the second preferable embodiment;

[0056]FIG. 6 is an explanatory diagram illustrating the secondmanufacturing process on manufacturing the heat conductive substrateaccording to the second preferable embodiment;

[0057]FIG. 7 is an explanatory diagram illustrating the thirdmanufacturing process on manufacturing the heat conductive substrateaccording to the second preferable embodiment;

[0058]FIG. 8 is an explanatory diagram illustrating the fourthmanufacturing process on manufacturing the heat conductive substrateaccording to the second preferable embodiment; and

[0059]FIG. 9 is a process section view illustrating a manufacturingprocess on manufacturing a heat conducting substrate according to aprior art.

DETAILED DESCRIPTION OF THE INVENTION

[0060] Preferable embodiments of the present invention are describedreferring to the drawings in the following.

[0061] A composition for substrate materials according to theembodiments comprises a mixture at least including 70 to 95 wt. % ofinorganic powder and 5 to 30 wt. % of thermosetting resin composition ofwhich the main component is thermosetting resin. In addition thismixture is processed to be in a powder condition or a granulated powdercondition or a granulation condition.

[0062] The inorganic powder is preferably coated with a thermosettingresin component and the thermosetting component is preferably in aB-stage condition. In case the inorganic powder is coated with thethermosetting resin composition, the adhesive properties betweeninorganic powder grains would be excellent. In case the thermosettingresin composition is in a B-stage condition, the handling would beeasier as the result of less stickiness of the component for substratematerials. The process manufacturing for the component for substratematerials is determined by the properties and conditions of the mixture.In the same way, the conditions exhibited by this composition forsubstrate materials after it is processed is determined by theproperties and conditions of the mixture.

[0063] Because of the following reasons the amount of the inorganicpowder in the composition for substrate materials is 70 to 95 wt. %. Incase the amount of inorganic powder is less that 70 wt. %, the heatconductivity of the mixture which is cured by being heated andpressurized is lowered to be improper as a material of a heat conductivesubstrate. If the amount of the inorganic powder is more than 95 wt. %,the filling amount of the thermosetting resin composition which combineswith the inorganic powder is lowered to have a worse mechanical strengthand insulation after being cured. Because of the above mentionedreasons, it is preferable for the amount of the inorganic powder to be70 - 95%, and more preferable to be 85 to 95 wt. %.

[0064] It is preferable for the inorganic powder to be at least one kindchosen from among Al₂O₃, MgO, BN and AlN. Those kinds of inorganicpowder could secure excellent heat conductivity.

[0065] It is preferable for the grain diameter of the inorganic powderto be within the range of 0.1 - 100 μm. Within this range, thedisadvantages would not occur such as deteriorated heat radiation, orwider thermal expansion coefficient difference between a heat conductivesubstrate and a semiconductor device and the like in a heat conductivesubstrate manufactured by utilizing this composition for substratematerials.

[0066] The thermosetting resin composition includes the following as themain component. That is to say, the thermosetting resin compositionincludes as least one kind of thermosetting resin chosen from amongepoxy resin, phenol resin and cyanate resin. In particular, thethermosetting resin composition includes a thermosetting resin havingbrominated polyfunctional epoxy resin as the main component. And in thiscase, the thermosetting resin component may include bisphenol A-typenovolac resin as a curing agent, and it may include imidazol as a curingaccelerator. Here imidazol is preferably micro-encapsulated. Themicro-encapsulated imidazol would secure an advantage that the storagestability of the composition for substrate materials is improved.Moreover, it is preferable to add to this heat setting resin component,at least one chosen among a coupling agent, a dispersing agent, acoloring agent and a mold-releasing agent.

[0067] A manufacturing process of a composition for substrate materialsaccording to the present embodiment is described based on the processdiagrams of FIGS. 1 - 4 in the following. FIGS. 1 - 4 illustrate the1^(st) to the 4^(th) manufacturing processes respectively applied uponmanufacturing a composition for substrate materials.

[0068] First of all, the first manufacturing process is describedreferring to FIG. 1. The first manufacturing process is in the casewhere the thermosetting resin which is the main component of thethermosetting composition is in a solid state at a room temperature. 70to 95% wt. of the inorganic powder and 5 to 30 wt. % of thermosettingresin composition are crushed into fine pieces and mixed to be processedinto a composition for substrate materials in a homogenized powdercondition. In this process, the inorganic powder and the thermosettingresin component may be crushed into fine pieces and mixed by utilizing aball mill and pulverizer or the like. By doing so, a composition forsubstrate materials in a homogenized powder condition is gained.

[0069] Next the second manufacturing process is described referring toFIG. 2. The second manufacturing process is in the case where thethermosetting resin which is the main component of the thermosettingresin composition is in a liquid condition at a room temperature.

[0070] 70 to 95 wt. % of the inorganic powder and 5 to 30 wt. % of thethermosetting resin composition are mixed to prepare a mixture. And theprepared mixture is granulated to be formed into a composition forsubstrate materials in a homogenized granulated powder condition.

[0071] According to this manufacturing process, lumps with uneven sizesare generated in the mixture because the thermosetting resin is in aliquid condition. Therefore the composition for substrate materials isgranulated by passing it through a mesh or by utilizing other methods tobe in a homogenized granulated powder condition. In mixing the inorganicpowder and thermosetting resin components, a ball mill, an automatedmortar or the like are used.

[0072] Next, the third manufacturing process is described referring toFIG. 3. The third manufacturing process is in the case where thethermosetting resin is in a liquid condition at a room temperature inthe same way as the second manufacturing process.

[0073] First of all, 70 to 95 wt. % of the inorganic powder and 5 to 30wt. % of the thermosetting resin composition including thermosettingresin in a liquid condition at a room temperature are mixed to prepare amixture. This mixture is heat-treated under the temperature conditionlower than the curing temperature of the heat setting resin to be turnedto a B-stage condition. In addition the prepared mixture is crushed andprocessed into a composition for substrate materials in a homogenizedpowder condition.

[0074] According to this manufacturing process, by turning thethermosetting resin composition into a B-stage condition the compositionfor substrate materials has less stickiness to be handled more easily.Temperature and time for heat treating the mixture are properlydetermined in accordance with the tackiness of the mixture and thedegree of curing of the thermosetting resin. And it is general to use aball mill or an automated mortar to crush the mixture into fine piecesafter the heat treatment.

[0075] Next, the fourth manufacturing process is described referring toFIG. 4. The fourth manufacturing process is a process that can beimplemented whether the thermosetting resin as the main component of thethermosetting resin composition is in a solid condition or in a liquidcondition at a room temperature.

[0076] First of all, a mixture is prepared by mixing 70 to 95 wt. % ofinorganic powder and 5 to 30 wt. % of thermosetting resin compositionincluding thermosetting resin together with solvent which can dissolvethe thermosetting resin. Then the solvent is removed by drying thismixture under a temperature condition lower than the curing temperatureof the thermosetting resin. And the dried mixture is crushed in to finepieces and processed into a composition for substrate materials in ahomogenized powder or granulation condition.

[0077] This manufacturing process secures the following advantages.First, a composition for substrate materials can be prepared with acertain process without being influenced by the condition of thethermosetting resin. And because good wettability is gained between theinorganic powder and the thermosetting resin composition through thesolvent, the thermosetting resin composition can be uniformly adhered tothe inorganic powder. In addition, an accompanying with the dryingprocess implemented to remove the solvent, the mixture becomeshalf-cured condition to be handled easily.

[0078] Though any solvent that can dissolve the thermosetting resincomposition can be used in this manufacturing process, it is preferableto be at least one kind chosen from among methyl ethyl ketone,isopropanol and toluene, and in general a ball mill, a planetary mixer,a stirring machine or the like are utilized when mixing. And though thetemperature and the required time in the drying process can be properlydetermined in accordance with the degree of solvent residue, tackinessof the mixture, the degree of curing of the thermosetting resin or thelike, it is preferable that the temperature is the boiling point of thesolvent or more and the curing temperature of the thermosetting resin orless. Moreover for the crushing treatment after the heat treatment, itis preferable to use a ball mill, an automated mortar or the like.

[0079] A composition for substrate material according to the presentembodiment is where inorganic powder is filled up in the thermosettingresin composition in high density and therefore can be utilized mostproperly in a process for a heat conductive substrate having a highconductivity.

[0080] And in a manufacturing process for a composition for substratematerials according to the present embodiment, thermosetting resin whichis in a liquid condition at a room temperature is used, is mixed withthe inorganic powder to turn this thermosetting resin into a B-stage sothat it can be handled easily. Then a solvent is added to thethermosetting resin composition to be mixed with the inorganic powder.Then, after that, it is dried for the solvent to be removed to gain acomposition for substrate materials where the thermosetting resin isadhered well to the inorganic powder.

[0081] (The second preferable embodiment)

[0082] A heat conductive substrate according to the present embodimentis provided with an insulator body formed by heating and pressurizingthe composition for substrate materials described in the firstembodiment, and a wiring pattern is formed on the insulator body. It ispreferable that the wiring pattern is a lead frame and a metal plate forheat radiation is attached integrally onto the insulator body. It goeswithout saying that the wiring pattern is not limited to a lead framebut may be a general thing formed by using a metal foil.

[0083] A process for manufacturing a heat conductive substrate accordingto the present embodiment is described in the following based oncross-sectional views showing the process of FIGS. 5 - 8. Those FIGS.5 - 8 respectively show the 1^(st)-4^(th) manufacturing processesapplicable for manufacturing a heat conductive substrate, and a heatconductive substrate with respect to the present embodiment may bemanufactured in accordance with those manufacturing processes. Andbefore manufacturing heat conductive substrate with respect to thesecond embodiment, either one of the manufacturing processes describedas the first embodiment should be first carried out to manufacture acomposition 11 for substrate materials.

[0084] In the first manufacturing process, as shown in FIG. 5A, apredetermined amount of the composition 11 for substrate materials iscast into a metal mold 13 where a lead frame 12 is arranged in advance.Then the composition 11 for substrate materials cast into the metal mold13 is heated and pressurized with a punch 14. Then the thermosettingresin in the thermosetting resin composition is once softened and thencured while combining inorganic powder grains together. By doing this,the composition 11 for substrate materials is turned into a heatconductive cured body 15. This heat conductive cured body 15 becomes aninsulator body. Moreover, the heat conductive cured body 15 isintegrated with the lead frame 12 when it is filled into every gap withthe lead frame 12 and cured, as a result it becomes a heat conductivesubstrate 16 shown in FIG. 5B. After processes are continued to modulateit through an electrode terminal process, a solder-resist process, aprocess for mounting parts or the like, but in those processes wellknown methods are applied, of which descriptions are omitted.

[0085] As for the lead frame 12, an alloy plate comprising, for example,copper, iron or both of them as the main material, is patterned to beutilized. As for the method of patterning, etching, stamping or the likegenerally used. And those lead frames 12 may be treated on the surfacewith surface protection treatment such as metal plating. As for thesurface treatment materials, nickel, solder, tin, palladium, gold or thelike are used. In addition, the pressure for heating and pressuringprocess is set in the range of 1-20 MPa and the temperature ispreferably in the range of 140-260° C. This is because of the followingreasons. In case the pressure is smaller than 1 MPa, the density of theheat conductive cured body 15 is lowered with deteriorated hermeticproperties and heat conductivity. On the other hand in case it is largerthan 20 MPa, the molded heat conductive cured body 15 can easily undergodamage. And in case the temperature for heating and pressurizing processis lower than 140° C., there is a danger that the thermosetting resincannot be fully cured. On the other hand if it is higher than 260° C.the thermosetting resin may start to be decomposed.

[0086] Next the second manufacturing process is described based on FIG.6. As shown in FIG. 6A, a projecting portion 17 is provided for inadvance in the metal mold 13. The lead frame 12 is contained andarranged in this metal mold 13, and then a predetermined amount of thecomposition 11 for substrate materials is cast into the metal mold 13.The composition 11 for substrate materials cast into the metal 13 isheated and pressurized with the punch 14. Then the composition 11 forsubstrate materials which was heated and pressurized is cured and moldedto the heat conductive cured body 15. This heat conductive cured body 15becomes an insulator body. Moreover, by integrating the heat conductivecured body 15 with the lead frame 12, a heat conductive substrate 18 isgained as shown in FIG. 6B. A recess portion 19 is formed on the surfaceof the heat conductive substrate 18 in the place facing the projectingportion 17 of the metal mold 13. This recess portion 19 is forelectronic parts or the like to be inserted.

[0087] In this way, according to the second manufacturing process, theheat conductive substrate 18 with a complicated shape can bemanufactured by using the composition 11 for substrate materials.

[0088] Next, the third manufacturing process is described based on FIG.7. In this manufacturing process, a metal plate 20 for heat radiation isarranged within the metal mold 13 and the metal plate 20 is alsocombined and integrated with the heat conductive substrate on forming aheat conductive substrate by combining the composition 11 for substratematerials and the lead frame 12.

[0089] In the third manufacturing process, as shown in FIG. 7A, apredetermined amount of the composition 11 for substrate materials isfirst cast into the metal mold 13 in which the lead frame 12 isarranged. After the composition 11 for substrate materials is cast, themetal plate 20 is arranged on the composition 11 for substrate materialswithin the metal mold 13. Then the composition 11 for substratematerials is heated and pressurized with the punch 14 through this metalplate 20, thereby the composition 11 for substrate materials is cured tobe the heat conductive cured body 15. On combining the heat conductivecured body 15 and the lead frame 12, the resulting combination mayinvolve the metal plate 20 to be a heat conductive substrate 21 as shownin FIG. 7B. In this heat conductive substrate 21, the lead frame 12 andthe metal plate 20 are integrated with the heat conductive cured body15. In addition for the metal plate 20, a copper plate or an aluminumplate can be used, and the heat conductive substrate 21 with such aconfiguration may increase the heat radiation properties or themechanical strength.

[0090] In addition, according to the fourth manufacturing process formanufacturing heat conductive substrate, as shown in FIG. 8A, apredetermined amount of the composition 11 for substrate materials iscast into the metal mold 13 in which the metal foil 22 is arranged inadvance. After the composition 11 for substrate materials is cast, ametal foil 22 is arranged on the composition 11 for substrate materialswithin the metal mold 13. Then through the upper one of the metal foils22, the composition 11 for substrate materials is heated and pressurizedwith the punch 14. Then the thermosetting resin in the composition 11for substrate materials is once softened and then cured while combininginorganic powder grains together. Thereby, the composition 11 forsubstrate materials turns to the heat conductive cured body 15, which isintegrated with the metal foils 22 adhered on both sides of this heatconductive cured body 15. Continuously those metal foils 22 arepatterned to form a heat conductive substrate 23 with a wiring patternformed thereon as shown in FIG. 8B.

[0091] As for the metal foils 22, copper foils or the like can beutilized. The thickness of the copper foil is preferable 12 - 200 μm. Incase the thickness is less than 12 μm, it is difficult to handle and iseasily broken. On the other hand in case the thickness is more than 200μm, it becomes difficult to pattern. In addition, the metal foils 22 arepreferably roughened on the surface facing the composition 11 forsubstrate materials. Being roughened would increase the adhesivestrength.

[0092] The metal foils 22 can be patterned by chemical etching utilizingiron chloride. And it goes without saying that on a completed heatconductive substrate 23, through-holes are formed and then wiringpatterns on both sides of the substrate may be electrically connectedwith each other. A process to be implemented on forming through-holes isfor example drilling. And an electric connection method viathrough-holes can be carried out with a well known method such as metalplating.

[0093] In accordance with a process for manufacturing a heat conductivesubstrate according to the present embodiment, it is possible tointegrate the inorganic powder and a lead frame after firmly combiningthe inorganic powder grains together by curing the thermosetting resinin the composition for substrate materials. Therefore, a heat conductivesubstrate with high heat radiation can be implemented in a simplemanner. And by using a composition for substrate materials according tothe present invention, a heat conductive substrate having a complicatedshape can be manufactured easily with high precision. And because it ispossible to integrate a metal plate for heat radiation at the same timeas molding if necessary, the further increased heat radiation of theheat conductive substrate can be implemented.

[0094] As describe above, a heat conductive substrate according to thepresent embodiment could have inorganic powder functioning as a fillerplaced in high density and therefore could secure a high heatconductivity conventional circuit substrates could not attain. Andbecause a composition for substrate materials in a powder or in agranulation conditions is used, a lead frame and a heat conductivesubstrate can be integrally molded with high precision even if the leadframe has a complicated shape. In addition such a molding with highprecision can be implemented in a simple process. The heat conductivesubstrate after being cured is rigid, mechanically firm and at the sametime has a heat conductivity equal to that of a ceramic substrate,therefore it is useful as a circuit substrate for mounting digital highspeed LSIs, which will be used increasingly in the future, for powercircuits or those generating high power loss.

[0095] The present invention will be described in further detail basedon concrete examples of applications as follows.

[0096] (Example of application 1)

[0097] Alumina bole is added to inorganic powder and thermosetting resincomposition in order to increase a dispersal condition, and then theresulting substance is mixed with a ball mill to prepare a compositionfor substrate materials such as those illustrated in Table 1, that is tosay, an Example 1a for comparison and Embodiments 1b-e are prepared.Table 1 shows examples in which the compounding ratio of inorganicpowder is varied. As inorganic powder, an alumina powder (trade name:AL-33, made by Sumitomo Chemical Co., Ltd, average grain diameter: 12μm) is used. As a thermosetting resin composition, a mixture of epoxyresin which is in a solid condition at a room temperature (trade name:EPICOAT 1010, made by Yuka Shell Epoxy Co., Ltd.) and a curing agent(trade name: CUREZOLE 2MZ, made by Shikoku Chemicals Corp.) with a ratioof 100:5 is used. TABLE 1 Thermosetting resin composition (including aInorganic powder curing agent) Substance Substance Number name wt. %name wt. % Example 1a for Al₂O₂ 60 Epoxy resin 40 comparison Embodiment1b 70 30 Embodiment 1c 80 20 Embodiment 1d 90 10 Embodiment 1e 95  5

[0098] Example 1a for comparison and embodiments 1b-e which havecompounding compositions in Table 1 are respectively weighed and mixedby rotating it in a pot with a velocity of 1500 rpm for a period of 24hours after the alumina bole is added. Next, compositions for substratematerials in Example 1a for comparison and Embodiments 1b-e are measuredin a predetermined amounts and cast into a metal mold, respectively, andcured under the conditions of 5 MPa and 200° C. to gain a cured body ina plate (thickness of about 0.8 mm). After processing each of the thusgained cured bodies into a predetermined dimension, the heatconductivity, the bending strength and the withstand voltage againstinsulation are measured. The resultant measurements are shown in Table2. TABLE 2 Withstand Heat Bending voltage against conductivity strengthinsulation Number (W/mK) (kgf/mm²) (kV/mm) Example 1a for 0.8 27 15comparison Embodiment 1b 1.2 24 14 Embodiment 1c 1.9 22 14 Embodiment 1d3.5 18 12 Embodiment 1e 4.1 13  9

[0099] The heat conductivity, the bending strength and the withstandvoltage against insulation are found as follows. The surface of a samplecut off 10 mm square is heated by a heater contacted directly on thesurface to find the heat conductivity by calculating the way thetemperature conveys to the opposite surface. And a test specimen withthe width of 15 mm is supported with two points spaced 25 mm apart, ofwhich central part is pressed in a certain velocity so that the bendingstrength is found by the strength when it is broken. And AC withstandvoltage is found in the direction of the thickness of a sample to findthe withstand voltage against insulation by calculating the result intothat per unit thickness. The bending strength and the withstand voltageagainst insulation relate greatly to the adhesion between thethermosetting resin compound and the inorganic powder, and in case thewettability between them is poor, microscopic gaps occur between them,and as a result, those characteristics are lowered. Therefore, thebending strength is determined to have enough strength when it is 10kgf/mm² or more. And since the withstand voltage against insulation forresin only is about 15 kV/mm, it is determined that good adhesion isgained in case the withstand voltage against insulation is 10 kV/mm ormore.

[0100] By the measurement result of Table 2, the following conclusionsare gained. That is to say, a cured body manufactured from each of thecompositions for substrate materials of Embodiments 1b-e would gain theheat conductivity which is about 10 times or more as large as that ofconventional printed wiring substrate shown as Example 1a for comparisonwithout lowering the bending strength or the withstand voltage againstinsulation. And in those embodiments, it is ensured that more thandouble performances (the heat conductivity or the like) can be exercisedcompared to a conventional injection molding method, though it is notshown. In this way it is understandable that a composition for substratematerials according to the present invention is suitable for aninsulation material for heat conductive substrates.

[0101] (Example of application 2)

[0102] Materials with the composition shown in Embodiments 2a-d in Table3 respectively are measured and mixed with a ball mill according to thesame method as Example 1 after the alumina bole is added. As forinorganic powder, alumina powder is used as was the case in Example 1.As for epoxy resin which is in a solid state at a room temperature, thesame resin is used as was the case in Example 1 (including a curingagent), and as epoxy resin which is in a liquid condition at roomtemperature, EPICOAT 828 (trade name, made by Yuka Shell Epoxy Co.,Ltd.) is used mixed with a curing agent (trade name: PN-23, made byAjinomoto Co., Inc.). In addition, in Embodiment 2d, methyl ethyl ketone(made by Kanto Chemical Co., Ltd.) is added in the proper amount as asolvent. This solvent is later evaporated in the air in the dryingprocess, which does not remain in the composition for substratematerials, and is not included in the compounding ratio calculation.TABLE 3 Thermosetting resin composition Embodi- Inorganic powder(including a curing agent) ment Substance Substance number name wt %name wt % Solvent 2a Al₂O₃ 90 Epoxy resin which 10 None is solid at aroom temperature 2b Epoxy resin which None is liquid at a roomtemperature 2c Epoxy resin which None is liquid at a room temperature 2dEpoxy resin which MEK is solid at a room temperature

[0103] In Embodiment 2a, as was the case in Example 1 described above,the composition for substrate materials is gained by rotating and mixingwith a ball mill. In Embodiment 2b, in the same way, the mixture gainedby rotating and mixing with a ball mill is sieved through 850 μm ofopening diameter to granulate and a composition for substrate materialsis gained. In Embodiment 2c, the same mixture gained by rotating andmixing is turned to a B-stage by leaving this mixture (thermosettingresin composition) as it is for 10 minutes at 80° C. Then the mixture ina B-stage is crushed into fine pieces in a mortar to gain a compositionfor substrate materials. In Embodiment 2d, the same mixture is gained byfirst rotating and mixing with a ball mill and then it is left as it isfor 20 minutes at 100° C. to evaporate the solvent in the mixture intothe air. And after that the mixture is crushed into fine pieces with amortar to gain a composition for substrate materials.

[0104] Compositions for substrate materials of those Embodiments 2a-dare cured in the same way as Example 1 to prepare cured bodies in aplate, of which the characteristics are measured. The resultantmeasurements are shown in Table 4. TABLE 4 Withstand Heat Bendingvoltage against Embodiment conductivity strength insulation number(W/mK) (kgf/mm²) (kV/mm) 2a 3.5 18 12 2b 3.5 19 13 2c 3.4 19 14 2d 3.721 14

[0105] According to the result of Table 4, it is understood that amixture gained by curing a composition for substrate materials is properas an insulation material for a heat conductive substrate. As for aprocess for manufacturing a composition for substrate materials, avariety of methods are applicable. Particularly as in the case ofEmbodiment 2d, it can be understood that the adhesive properties amonginorganic powder grains are particularly excellent, and as a result, theheat conductivity is efficient as well as the bending strength and thewithstand voltage against insulation are also high.

[0106] (Example of application 3)

[0107] Using a composition for substrate materials manufacturedaccording to a process of Example 2, Example 3 of a heat conductivesubstrate integrated with a lead frame is described. In this Example 3,a composition for substrate materials comprising:

[0108] inorganic powder: Al₂O₃ (trade name: AS-40, made by Showa DenkoK.K., spherical grains with the average grain diameter of 12 μm), 90 wt.part

[0109] thermosetting resin: cyanate ester resin (trade name: AroCy M30,made by Asahi Ciba Co., Ltd.), 9.5 wt. part

[0110] other additives: carbon black (made by Toyo Carbon Co., Ltd.) 0.3wt. part and dispersing agent (trade name: PLYSURF A208F, made byDai-Ichi Kogyo Seiyaku Co., Ltd.), 0.2 wt. part.

[0111] is used.

[0112] A lead frame is prepared by processing a copper plate with athickness of 500 μm by etching and nickel plating and then this leadframe is arranged within a metal mold as shown in FIG. 6A. Then acomposition for substrate materials described above is cast into themetal mold in which the lead frame is arranged. Continuously thecomposition for substrate materials within the metal mold is heated andpressurized under the conditions of 5 MPa and 175° C. so that thecomposition for substrate materials flows into the gaps with the leadframe before curing. Thereby a heat conductive substrate integrated withthe lead frame is gained as shown in FIG. 6B.

[0113] The outer periphery of the lead frame of this heat conductivesubstrate is cut off, and the bending process of the terminals iscarried out and the heat conductivity is measured. The resultantmeasurement shows the value of 3.7 W/mK to make sure that the gainedheat conductivity is about twice as large as that gained in general forconventional injection molding or metal-based substrates.

[0114] For this example, a reflow test is carried out for 10 seconds atthe maximum temperature of 260° C. as a reliability evaluation test.And, after that, adhesion at the interface between the substrate and thelead frame is detected by a supersonic inspection image device. As aresult, no abnormality is recognized at the interface between thesubstrate and the lead frame to make sure that it has firm adhesion.

[0115] (Example of application 4)

[0116] Using a composition for substrate materials manufactured in thesame way as Embodiment 2d described above, an example of a heatconductive substrate in which a lead frame and a metal plate areintegrated is described. In the present example:

[0117] inorganic powder: Al₂O₃ (trade name: AS-40, made by Showa DenkoK.K., spherical grains with the average grain diameter of 12 μm), 90 wt.part

[0118] thermosetting resin: brominated epoxy resin (trade name:NVR-1010, made by Nihon Rec Co., Ltd.), 9 wt. part

[0119] other additives,

[0120] methyl ethyl ketone as a solvent

[0121] are prepared.

[0122] As for the above mentioned other additives,

[0123] curing accelerator (imidazol, made by Nihon Rec Co., Ltd.) 0.05wt. part,

[0124] carbon black (made by Toyo Carbon Co., Ltd.) 0.4 wt. part

[0125] coupling agent (PRENACT KR-46B, made by Ajinomoto Co., Inc.) 0.55wt. part,

[0126] are prepared.

[0127] As for methyl ethyl ketone, 10 wt. part to 100 wt. part ofinorganic powder is prepared.

[0128] First of all, the materials comprising inorganic powder,thermosetting resin and other additives are mixed after methyl ethylketone, which is a solvent, is added. Then this mixture is dried for 20minutes at 100° C. to evaporate methyl ethyl ketone into the air, andafter that, it is crushed into fine pieces to prepare a composition forsubstrate materials.

[0129] On the other hand, the same lead frame as Example 3 is preparedand a metal plate gained by punching out an aluminum plate with athickness of 300 μm is prepared. Then as shown in FIG. 7A, a lead frameis arranged within the metal mold before the composition for substratematerials is cast and a metal plate is arranged on the top side of thecast composition for substrate materials. After that, the compositionfor substrate materials within the metal mold is heated and pressurizedthrough the metal plate under the conditions of 5 MPa and 175° C. sothat the composition for substrate materials flows into gaps of the leadframe and then cured. Thereby, a heat conductive substrate integratedwith the lead frame is gained as shown in FIG. 7B.

[0130] The outer periphery of the lead frame of this heat conductiveframe is cut off and the bending process of the terminals is carried outto measure the heat conductivity. The resultant measurement indicatesthe value of 4.2 W/mK to make sure that the gained heat conductivity isabout twice as large as the heat conductivity gained generally forconventional injection molding methods or metal-based substrates. Inaddition, since a metal plate functioning as a heat radiation plate isintegrated and attached, the heat resistance is greatly lowered comparedto the case without a metal plate.

[0131] And for this example, a reflow test is carried out for 10 secondsat the maximum temperature of 260° C. as a reliability evaluation test.After that, the adhesion at the interface between the substrate and thelead frame is detected by a supersonic inspection image device. As aresult, no abnormality is recognized at the interface between thesubstrate and the lead frame to make sure that the adhesion is firm.

[0132] (Example of application 5)

[0133] Using a composition for substrate materials manufactured in thesame way as Embodiment 2b shown in Example 2, an example of heatconductive substrate, on both sides of which a wiring pattern comprisinga metal foil is formed, is described. In this Example 5:

[0134] inorganic powder: Al₂O₃ (trade name: AM-28, made by SumitomoChemical Co., Ltd., spherical grains with the average grain diameter of12 μm), 90 wt. part

[0135] thermosetting resin: phenol resin (trade name: PHENOLITE VH4150,made by Dainippon Ink & Chemicals, Inc.), 9.5 wt. part

[0136] other additives,

[0137] are prepared.

[0138] As for the above mentioned other additives,

[0139] carbon black (made by Toyo Carbon Co., Ltd.) 0.3 wt. part,

[0140] coupling agent (trade name: PLENACT KR-55, made by Ajinomoto Co.,Inc.), 0.2 wt. part,

[0141] are prepared.

[0142] By mixing those materials and by sieving the mixture through 600μm of opening diameter to granulate, a composition for substratematerials in a granulated powder condition is prepared.

[0143] Except for those materials, a copper foil with a thickness of 35μm, one side of which is roughened is prepared as a metal foil.

[0144] First of all, as shown in FIG. 8A, a copper foil is arrangewithin the metal mold with its roughened surface above so that theroughened surface touches on the composition for substrate materials.Then the above composition for substrate materials is cast into themetal mold and then another copper foil is arranged on the upper side ofthe composition for substrate materials within the metal mold so thatthe roughened surface touches on the composition for substratematerials. After that, the composition for substrate materials withinthe metal mold is cured by heating and pressurizing through the copperfoil under the conditions of 3 MPa and 180° C. so that at the same timethe copper foils are integrated into the composition for substratematerials, respectively. Thereby, a heat conductive substrate shown inFIG. 8B is formed. In this case, the heat conductive cured body and theroughened surface of the copper foils are firmly adhered because phenolresin in the composition for substrate materials is cured.

[0145] After that, through-holes with the diameter of 0.3 mm are formedby a drill in the heat conductive substrate integrating the copperfoils, on which the copper plating with the thickness of abort 20 μm iscarried out for the entire surface including the through-holes. And theunnecessary parts of the copper foils are removed by etching to gain theheat conductive substrate.

[0146] The heat conductivity of this heat conductive substrate ismeasured. The resultant measurement indicates the value of 3.3 W/mK tomake sure that the gained heat conductivity is nearly twice as large asthe heat conductivity generally gained for the heat conductivesubstrates or metal-based substrates based on conventional injectionmolding methods.

[0147] For this example, a reflow test is carried out for 10 seconds atthe maximum temperature of 260° C. as a reliability evaluate test todetect the adhesion at the interface between the substrate and the leadframe by a supersonic image inspection device. As a result noabnormality is recognized at the interface between the substrate and thelead frame to make sure that the adhesion is firm.

[0148] The present invention is described in detail with respect to themost favorite embodiments, but combinations and arrangements of theparts regarding the favorite embodiments can be modified in a variety ofways without deviating from the spirit and scope of this invention whichis claimed in the following.

What is claimed is:
 1. A composition for substrate materials including70 - 95 wt. % of inorganic powder having electrical insulation and 5 -30 wt. % of thermosetting resin composition and being in a finelycrushed condition.
 2. A composition for substrate materials according toclaim 1 , wherein said composition is in a powder condition.
 3. Acomposition for substrate materials according to claim 1 , wherein saidcomposition is in a granulation condition.
 4. A composition forsubstrate materials according to claim 2 , wherein said thermosettingresin composition is in a liquid condition at a room temperature and theentire composition including this thermosetting resin composition is ina powder condition.
 5. A composition for substrate materials accordingto claim 3 , wherein said thermosetting resin composition is in a liquidcondition at a room temperature and the entire composition includingthis thermosetting resin composition is in a granulation condition.
 6. Acomposition for substrate materials according to claim 1 , wherein saidinorganic powder is coated with said thermosetting resin composition. 7.A composition for substrate materials according to claim 6 , whereinsaid thermosetting composition is in a B-stage condition.
 8. Acomposition for substrate materials according to claim 1 , wherein saidinorganic powder is at least one kind chosen from among Al₂O₃, MgO, BNand AlN.
 9. A composition for substrate materials according to claim 1 ,wherein said inorganic powder has a grain diameter in a range of 0.1 -100 μm.
 10. A composition for substrate materials according to claim 1 ,wherein said thermosetting resin composition includes as a maincomponent at least one kind of thermosetting resin chosen from amongepoxy resin, phenol resin and cyanate resin.
 11. A composition forsubstrate materials according to claim 10 , wherein said thermosettingresin composition includes brominated polyfunctional epoxy resin as amain component, and further includes bisphenol A-type novolac resin as acuring agent and imidazol as a curing accelerator.
 12. A composition forsubstrate materials according to claim 11 , wherein said imidazol ismicro-encapsulated.
 13. A composition for substrate materials accordingto claim 10 , wherein at least one kind chosen from among a couplingagent, a dispersing agent, a coloring agent and a mold-releasing agentis added to said thermosetting resin composition.
 14. A process formanufacturing a composition for substrate materials, wherein 70 - 95 wt.% of inorganic powder and 5 - 30 wt. % of thermosetting resincomposition including thermosetting resin which is in a solid conditionat a room temperature are crushed into fine pieces and mixed.
 15. Aprocess for manufacturing a composition for substrate materials,comprising the steps of: 70 - 95 wt. % of inorganic powder and 5 - 30wt. % of thermosetting resin composition including a thermosetting resinwhich is in a liquid condition at a room temperature are mixed; and amixture prepared at the foregoing step is granulated and crushed intofine pieces.
 16. A process for manufacturing a composition for substratematerials comprising the steps of: 70 - 95 wt. % of inorganic powder and5 - 30 wt. % of thermosetting resin composition including athermosetting resin which is in a liquid condition at a room temperatureare mixed; said thermosetting resin composition is turned into a B-stageby heat treating a mixture prepared at the foregoing step under atemperature condition lower than a curing temperature of saidthermosetting resin; and said mixture gained as the B-stage into whichsaid thermosetting resin composition is turned is crushed into finepieces.
 17. A process for manufacturing a composition for substratematerials comprising the steps of: 70 - 95 wt. % of inorganic powder and5 - 30 wt. % of thermosetting resin composition including athermosetting resin are mixed with a solvent in which said thermosettingresin is solved; a mixture processed at the foregoing step is dried at atemperature lower than a curing temperature of said thermosetting resinto remove said solvent from said mixture; and said mixture from whichsaid solvent is removed is crushed into fine pieces.
 18. A process formanufacturing a composition for substrate materials according to claim17 wherein said solvent includes at least one kind chosen from amongmethyl ethyl ketone, isopropanol and toluene.
 19. A heat conductivesubstrate having an insulator body formed by heating and pressurizing acomposition for substrate materials including 70 - 95 wt. % of inorganicpowder having electric insulation and 5 - 30 wt. % of thermosettingresin composition and being in a finely crushed condition.
 20. A heatconductive substrate according to claim 19 , wherein a wiring pattern isprovided in such a condition that it is exposed on a surface of saidinsulator body.
 21. A heat conductive substrate according to claim 20 ,wherein said wiring pattern is a lead frame.
 22. A heat conductivesubstrate according to claim 19 , wherein a metal plate for heatradiation is provided in such a condition that it is exposed on asurface of said insulator body.
 23. A process for manufacturing a heatconductive substrate comprising: the first step that a composition forsubstrate materials including 70 - 95 wt. % of inorganic powder havingelectric insulation and 5 - 30 wt. % of thermosetting resin compositionand being in a finely crushed condition is cast into a metal mold; andthe second step that said composition for substrate materials is formedinto a insulator body by heating and pressurizing said composition forsubstrate materials within said metal mold so that said thermosettingresin is cured.
 24. A process for manufacturing a heat conductivesubstrate according to claim 23 , wherein a pressure when saidcomposition for substrate materials is heated and pressurized is in arange of 1 - 20 MPa.
 25. A process for manufacturing a heat conductivesubstrate according to claim 23 , wherein a temperature when saidcomposition for substrate materials is heated and pressurized is in arange of 140 - 260° C.
 26. A process for manufacturing a heat conductivesubstrate according to claim 23 , wherein: in said first step, a leadframe is arranged in advance within said metal mold, and then saidcomposition for substrate materials is cast into said metal mold; and insaid second step, said insulator body and said lead frame are integrallymolded by heating and pressurizing said composition for substratematerials.
 27. A process for manufacturing a heat conductive substrateaccording to claim 26 , wherein: in said first step, a metal plate forheat radiation is arranged within said metal mold into which saidcomposition for substrate materials is cast; and in said second step,said insulator body and said metal plate are integrally molded byheating and pressurizing said composition for substrate materials.
 28. Aprocess for manufacturing a heat conductive substrate according to claim23 , wherein: in said first step, a metal foil is arranged in advancewithin said metal mold, and then said composition for substratematerials is cast into within said metal mold; and in said second step,said insulator body and said metal foil is integrally molded by heatingand pressurizing said composition for substrate materials, and then saidmetal foil is pattern-processed into a wiring pattern.
 29. A process formanufacturing a heat conductive substrate according to claim 28 ,wherein said metal foil is copper foils having a thickness of 12 - 200μm of which surface is roughened at least in a part facing thecomposition for substrate materials.
 30. A process for manufacturing aheat conductive substrate according to claim 28 , wherein: in said firststep, a metal foil is arranged within said metal mold into which saidcomposition for substrate materials is cast; and in said second step,said insulator body and said metal foil are integrally molded by heatingand pressurizing said composition for substrate materials, and thenthese metal foil is pattern-processed into a wiring pattern.